A uniform color space based on color vision mechanisms was proposed. The mechanisms considered to construct the uniform color space were, proportion of three types of cones, compressive response nonlinearity at receptor and post- receptor stages, constant noise or dark response added to the receptor response, and fractional expressions of opponent and S channel in the postreceptor stage. The present uniform color space explains, three dimensional color discrimination data, supra-threshold color differences such as Munsell color chips, and luminance dependence of the color differences.